1. Technical Field
The present invention relates to a technology for incising or excising living tissue by ejecting pressurized liquid toward the living tissue.
2. Related Art
A technology for incising or excising tissue or the like by pressurizing liquid such as water or physiologic saline and ejecting the liquid from an ejection nozzle toward the living tissue in a restricted state is developed (JP-A-2005-152127). This technology enables incision of tissue such as internal organ exclusively without damaging vascular structures such as blood vessels, and causes less damage to peripheral tissues. Therefore, burdens on patients can be reduced.
There is also proposed a technology configured to eject a pulsed jet stream intermittently when ejecting liquid instead of ejecting continuously from an ejection nozzle. In this proposed technology, liquid is supplied to a small liquid chamber connected to the ejection nozzle and reduces the volume of the liquid chamber instantaneously, thereby ejecting liquid from the ejection nozzle in a pulsed manner. Subsequently, the volume of the liquid chamber is restored and the liquid is supplied again. By repeating such actions, the pulsed jet stream is ejected intermittently. In this manner, by ejecting the pulsed jet stream, the pressure of the jet stream is impulsively applied to the living tissue, and hence the living tissue can be incised with a small amount of ejection. Consequently, such events that the visibility of the living tissue to be incised is lowered due to the ejected liquid accumulated therearound or the force of the jet stream is damped by the accumulated liquid and hence the incising capability is lowered can be restrained (JP-A-2008-082202).
However, in the technology for ejecting the liquid in a pulsed manner, there is a problem such that keeping the stable incising capability is difficult. In other words, since the pulsed jet stream is ejected by pressurizing the liquid by reducing the volume of the liquid chamber instantaneously, if air bubbles get into the liquid chamber, the air bubbles are compressed, and hence the liquid cannot be pressurized sufficiently. Consequently, the incising capability is lowered. When the jet stream is apparently slowed due to too many air bubbles trapped therein, the incising capability may be restored by removing the trapped air bubbles. However, when the quantity of bubbles got into the liquid chamber is small, an operator cannot recognize that the air bubbles are trapped and hence continues to use the device with the lowered incising capability.